Jin-Yue Gao

Observation of light amplification without population inversion in sodium

Abstract We discuss the results of experiments on the amplification of visible electromagnetic radiation without population inversion using sodium vapor as the active medium. The main result of this work is the amplification of a weak probe beam at a wavelength of 589.0 nm in the presence of an intense, pulsed, coherent driving field at 589.6 nm.

SHG phase matching in GaSe and mixed GaSe 1-x S x , x≤0.412, crystals at room temperature

The optical properties of p-type GaSe and mixed GaSe(1-x)S(x), x=0.04, 0.023, 0.090, 0.133, 0.175, 0.216, 0.256, 0.362, 0.369, and 0.412, crystals were studied to reveal the potentials for phase matching and frequency conversion. Comparative experiment on Er3+:YSGG and CO2 laser SHG at identical experimental conditions is carried out at room temperature. Any change in polytype structure of GaSe1(1-x)S(x) was not found.

Two-dimensional atom localization via interacting double-dark resonances

A scheme of two-dimensional (2D) atom localization based on the interference of double-dark resonances is proposed, in which the N-type atom interacts with two orthogonal standing-wave fields. Because of the spatial-dependent atom–field interaction, 2D atom localization can be realized via measuring the upper state population or the probe absorption. We obtain that the maximum probability of finding an atom at a particular position in a wavelength domain (λ1×λ2) is 1/2 when the atom is localized at the intersection of the antinodes of quadrants I and III of the standing-wave plane. This scheme shows more advantages than other schemes of 2D atom localization.

Two-dimensional atom localization via controlled spontaneous emission from a driven tripod system

A scheme for two-dimensional (2D) subwavelength atom localization is proposed, in which the atom is in a four-level tripod configuration and driven by two orthogonal standing-wave lasers. Because of the spatial dependence of atom-field interaction, the spontaneously emitted photon carries information about the position of the atom in standing-wave fields. We exploit this fact to 2D atom localization conditioned on the measurement of spontaneously emitted photon at a particular frequency, and obtain a high precision and resolution in the position probability distribution. Moreover, an improvement by a factor of 2 in the detecting probability of an atom can be achieved by initially preparing the atom in the coherent population trapping state. Qualitatively, the high-precision, high-resolution atom localization can be attributed to the quantum interference effect between competitive multiple spontaneous decay channels.

Investigation of spontaneously generated coherence in dressed states of 85 Rb atoms

We investigate the effects of spontaneously generated coherence (SGC) on the electromagnetically induced transparency features in a four-level Lambda-type system. We show that double-transparency windows and a controllable narrow absorption peak can be obtained with the presence of SGC. We present an equivalent system without the rigorous requirement of close-lying levels to observe the phenomena. We also experimentally demonstrate the corresponding features in a rubidium atomic beam.

All-optical routing by light storage in a Pr3+:Y2SiO5 crystal

We experimentally demonstrate an all-optical routing based on light storage in a Pr3+:Y2SiO5 crystal. Under electromagnetically induced transparency, the optical information of the probe light pulse can be stored in the crystal. By simultaneously switching on two retrieve control fields in the release process, the stored optical information from one light channel can be distributed into two light channels. Such an all-optical routing in solids may have practical applications in quantum information and all-optical network.

Simulating spontaneously generated coherence in a four-level atomic system

We study the spontaneous emission property of a four-level atomic system driven by two coherent fields. By numerical calculations in the bare state picture, we show that such interesting phenomena as extremely narrow peaks and spontaneous emission quenching can be realized, which are well understood by qualitative explanations in the partially and fully dressed state pictures. Especially, this coherently driven atomic system has two close-lying levels in the partially dressed state picture so that spontaneously generated coherence arises. Using our considered scheme it is feasible to carry out experiments based on spontaneously generated coherence because all rigorous requirements have been avoided in the bare state picture.

Erasure of stored optical information in a Pr3+:Y2SiO5 crystal

We experimentally demonstrate an erasure of stored optical information in a Pr3+:Y2SiO5 crystal by applying an erasing pulse to destroy atomic spin coherence. We observed an erasing efficiency of about 85%. Such an erasing operation of stored optical information may have practical applications in the field of information processing and all-optical network.

Wide-tunable, high-energy AgGaS 2 optical parametric oscillator

Nanosecond AgGaS(2) type-I singly resonant optical parametric oscillator pumped by a Q-switched 1.064 mum Nd:YAG laser is demonstrated experimentally. Continuously tunable 2.6-5.3 mum radiation and output pulse energy up to 0.6 mJ at 4 mum are achieved in a single-stage conversion process. The analysis of pump threshold is investigated both theoretically and experimentally.

Phase-dependent properties for absorption and dispersion by spontaneously generated coherence in a four-level atomic system

A four-level atomic system with two closely lying upper levels driven by two coherent fields is considered. We show that, in the presence of a weak incoherent pump, steady-state gain can be achieved as a result of quantum interference from spontaneous emission. The gain depends on the relative phase between the two fields, so it can be modulated by control of the relative phase. Also, by controlling the relative phase, one can always obtain a large index of refraction with zero absorption.